Rf amplifier system with interface to provide a computer readable spectral depiction of the rf output

ABSTRACT

An RF amplifier system includes an RF power amplifier, a coupler, a digital signal analysis circuit, and an interface. The RF power amplifier has an RF output. The coupler is coupled to the RF power amplifier to detect the RF output. The digital signal analysis circuit is coupled to the coupler to produce a digital signal that provides a spectral depiction of the RF output. The interface is coupled to the digital signal analysis circuit to provide the spectral depiction of the RF output to an attached computer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/362,295, filed Mar. 6, 2002 and of U.S. Provisional Application No.60/362,503, filed Mar. 6, 2002.

BACKGROUND OF THE INVENTION

RF amplifier systems may be used to amplify radio frequency (RF) signalsfor over the air broadcasting. RF amplifier systems are used at cellulartelephone sites which may be in remote locations. It may be necessary tomonitor the output of an RF amplifier system to ensure that it isperforming properly and in compliance with applicable broadcastingregulations. It may be very costly to dispatch a technician to a remotesite for routine testing. Even if the site of the RF amplifier system isconvenient, it is costly and time consuming to dispatch a technicianwith the necessary skills to correctly test the output of an RFamplifier system. These limitations may cause the RF amplifier system tooperate improperly or out of compliance for a substantial period of timeuntil a technician visits the site of the RF amplifier system to monitorthe output of the system.

SUMMARY OF THE INVENTION

An RF amplifier system includes an RF power amplifier, a coupler, adigital signal analysis circuit, and an interface. The RF poweramplifier has an RF output. The coupler is coupled to the RF poweramplifier to detect the RF output. The digital signal analysis circuitis coupled to the coupler to produce a digital signal that provides aspectral depiction of the RF output. The interface is coupled to thedigital signal analysis circuit to provide the spectral depiction of theRF output to an attached computer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block circuit diagram of an exemplary RF amplifier systemthat embodies the present invention.

FIG. 2 is a block circuit diagram of another exemplary RF amplifiersystem that embodies the present invention.

FIG. 3 is a block circuit diagram of an exemplary digital signalanalysis circuit that may be used in an embodiment of the presentinvention.

FIG. 4 is a block circuit diagram of another exemplary digital signalanalysis circuit that may be used in an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an RF amplifier system 10 that embodies the presentinvention. The RF amplifier system 10 receives an RF input 12 andproduces an RF output 16 that is the result of amplifying the RF inputwith an RF power amplifier 14. A coupler 18 detects the output 16 of theRF power amplifier 14 and feeds the detected signal into a digitalanalysis circuit 20 that produces a digital analysis of the spectraloutput of the RF power amplifier 14.

The digital analysis produced by the digital analysis circuit 20 is thenconverted by a computer interface 22 to a form that can be read by acomputer connected to the interface output 24. The computer may displayor print an X vs. Y plot of the output of the digital signal analysiscircuitry to provide a spectral depiction of the output of the RF poweramplifier 14. By integrating the RF power amplifier 14, the coupler 18,the digital analysis circuit 20, and the computer interface 22 in thesingle chassis of the RF amplifier system 10, the proper selection ofcoupler and analysis circuit for the RF power amplifier and the properconnection is assured. This may allow maintenance and servicing of theRF amplifier system 10 more quickly and by technicians with a lowerskill requirement.

FIG. 2 shows another RF amplifier system 11 that embodies the presentinvention. In this embodiment the digital analysis produced by thedigital analysis circuit 20 is converted by an Internet Protocol (IP)interface 26 to a form that can be communicated over long distances onthe internet by coupling the interface output 28 to the internet. Aremotely located computer may access the RF amplifier system 11 using aninternet connection to read, display, or print a spectral depiction ofthe output of that RF power amplifier 14. This may allow the operationof the RF amplifier system 11 to be monitored for correct operationwithout the need to send a technician to the site of the RF amplifiersystem on a routine basis. Remote monitoring may allow an initialdiagnosis of detected faults so that a properly equipped technician canbe dispatched to effect a repair of the RF amplifier system 11. A singleRF amplifier system may include both the computer interface 22 and theIP interface 26 and provide both the computer interface output 24 forlocal service and the IP interface output 28 for remote monitoring.

FIG. 3 shows an exemplary embodiment of the digital analysis circuit 20.The detected signal 30 from the coupler 18 (FIGS. 1 and 2) is mixed downin frequency via a voltage controlled oscillator (VCO) 32, a mixer 34,and a filter 36. A ramp generator 38 feeds the VCO 32 with a varyingvoltage. The output of the filter 36 is coupled to a log detector 40.

The resulting analog output of the log detector 40 is digitallyconverted via a low speed, low cost analog-to-digital (A/D) converter 42to provide a “Y” (magnitude) portion of an output signal 44a. The analogDC voltage output of the ramp generator 18 that is provided to the VCO32 is also converted via a second low speed, low cost, A/D converter 46to provide an “X” (frequency) portion of the output signal 44 b. An Xvs. Y plot of the output signal 44 from the digital analysis circuit 20,via electrical or mechanical means, may result in a spectral depictionof the RF output 16 of the RF amplifier system.

FIG. 4 shows another exemplary embodiment of the digital analysiscircuit 20. In this embodiment, the detected signal 30 from the coupler18 is mixed down with the signal from the VCO 32 as in the previousembodiment. A microprocessor 48 or controller instructs the rampgenerator 38′ to additionally output a blanking or “0” signal 50 of aknown interval simultaneously with the zero VDC point of the signal fromthe ramp generator 38′. The blanking signal 50 is fed into the output ofthe log detector 40. The resulting analog output of the log detector 40is digitally converted via a low speed, low cost A/D converter 42 tobecome the “Y” (magnitude+time) output signal 44. The blanking signalcontained within the Y (magnitude+time) output may then be extracted andused to represent the flow of the X (time) portion of an X vs. Y plotthat is a spectral depiction of the RF output 16 of the RF amplifiersystem.

An RF amplifier system 10 that embodies the present invention may permitlocal or remote monitoring of the RF output for overall or per-channelpower output, spurious signals or other forms of distortion, or to checkany other performance parameter where the information is containedwithin the spectral depiction. The invention may further permit local orremote monitoring of the RF output of a cellular telephone site forconformance to power output, emissions mask specifications, or to checkany other performance parameter where the information is contained withthe spectral depiction.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat this invention not be limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those ordinarily skilled in the art.

1. An RF amplifier system comprising: an RF power amplifier having an RFoutput; a coupler coupled to the RF power amplifier to detect the RFoutput; a digital signal analysis circuit coupled to the coupler toproduce a digital signal that provides a spectral depiction of the RFoutput; and an interface coupled to the digital signal analysis circuitto provide the spectral depiction of the RF output to an attachedcomputer.
 2. The RF amplifier system of claim 1, wherein the digitalsignal analysis circuit further comprises: a ramp generator; a voltagecontrolled oscillator (VCO) coupled to the ramp generator; a mixercoupled to the coupler and to the VCO; a filter coupled to the mixer; alog detector coupled to the filter; and an analog-to-digital convertercoupled to the log detector.
 3. The RF amplifier system of claim 2,wherein the digital signal analysis circuit further comprises a secondanalog-to-digital converter coupled to the ramp generator in parallelwith the VCO.
 4. The RF amplifier system of claim 2, wherein the rampgenerator is further coupled to the analog-to-digital converter and theramp generator produces a blanking signal of a known intervalsimultaneously with a zero VDC point of a signal from the ramp generatorthat is fed into the output of the log detector.
 5. The RF amplifiersystem of claim 4, further comprising a microprocessor that is coupledto the ramp generator to control the production of the blanking signal.6. The RF amplifier system of claim 1, wherein the interface is acomputer interface to provide the spectral depiction of the RF outputthat can be read by a connected computer.
 7. The RF amplifier system ofclaim 1, wherein the interface is an internet interface to provide thespectral depiction of the RF output that can be read by a computerconnected to the interface output by an internet connection.
 8. A methodof providing an a spectral depiction of an RF output from an RFamplifier system, the method comprising: coupling to the RF output of anRF power amplifier in the RF amplifier system to detect the RF output;performing digital signal analysis to produce a digital signal thatprovides a spectral depiction of the RF output; and providing aninterface on the RF amplifier system that allows a computer to beconnected to the RF amplifier system to obtain the spectral depiction ofthe RF output.
 9. The method of claim 8, wherein performing digitalsignal analysis further comprises: generating a ramp voltage;controlling a frequency of an oscillator signal with the ramp voltage;mixing the detected RF output with the oscillator signal to produce amixed signal; filtering the mixed signal; logarithmically detecting thefiltered signal; and converting the analog logarithmically detectedsignal to the spectral depiction of the RF output.
 10. The method ofclaim 9, wherein performing digital signal analysis further comprisesconverting the ramp voltage to the spectral depiction of the RF output.11. The method of claim 9, wherein performing digital signal analysisfurther comprises producing a blanking signal of a known intervalsimultaneously with a zero VDC point of the ramp voltage and feeding theblanking signal into the logarithmically detected signal.
 12. The methodof claim 8, wherein providing an interface on the RF amplifier systemprovides the spectral depiction of the RF output that can be read by aconnected computer.
 13. The method of claim 8, wherein providing aninterface on the RF amplifier system provides the spectral depiction ofthe RF output that can be read by a computer connected to the interfaceoutput by an internet connection.
 14. An RF amplifier system comprising:an RF power amplifier means for producing an RF output; a first meanscoupled to the RF power amplifier means for detecting the RF output; asecond means coupled to the first means for producing a digital signalthat provides a spectral depiction of the RF output; and a third meanscoupled to the third means for providing the spectral depiction of theRF output to an attached computer.
 15. The RF amplifier system of claim14, wherein the second means further comprises: a ramp generator meansfor generating a ramp voltage; a voltage controlled oscillator (VCO)means coupled to the ramp generator means for controlling a frequency ofan oscillator signal with the ramp voltage; a mixer means coupled to thefirst means and to the VCO means for mixing the detected RF output withthe oscillator signal to produce a mixed signal; a filter means coupledto the mixer means for filtering the mixed signal; a log detector meanscoupled to the filter means for logarithmically detecting the filteredsignal; and an analog-to-digital converter means coupled to the logdetector means for converting the analog logarithmically detected signalto the spectral depiction of the RF output.
 16. The RF amplifier systemof claim 15, wherein the second means further comprises a secondanalog-to-digital converter means coupled to the ramp generator means inparallel with the VCO means for converting the ramp voltage to thespectral depiction of the RF output.
 17. The RF amplifier system ofclaim 15, wherein the ramp generator means is further coupled to theanalog-to-digital converter means and the ramp generator means isfurther for producing a blanking signal of a known intervalsimultaneously with a zero VDC point of a signal from the ramp generatormeans that is fed into the output of the log detector means.
 18. The RFamplifier system of claim 17, further comprising a microprocessor meansthat is coupled to the ramp generator means for controlling theproducing of the blanking signal.
 19. The RF amplifier system of claim14, wherein the third means is for providing the spectral depiction ofthe RF output that can be read by a connected computer.
 20. The RFamplifier system of claim 14, wherein the third means is for providingthe spectral depiction of the RF output that can be read by a computerconnected to the interface output by an internet connection.
 21. An RFamplifier system comprising: an RF power amplifier means for producingan RF output; a first means for coupling to the RF output to detect theRF output; a second means for performing digital signal analysis toproduce a digital signal that provides a spectral depiction of the RFoutput; and a third means for providing an interface on the RF amplifiersystem that allows a computer to be connected to the RF amplifier systemto obtain the spectral depiction of the RF output.
 22. The RF amplifiersystem of claim 21, wherein the second means further comprises: a rampgenerator means for generating a ramp voltage; a voltage controlledoscillator (VCO) means for coupling to the ramp generator means tocontrol a frequency of an oscillator signal with the ramp voltage; amixer means for coupling to the first means and to the VCO means toproduce a mixed signal; a filter means for coupling to the mixer meansto filter the mixed signal; a log detector means for coupling to thefilter means to logarithmically detect the filtered signal; and ananalog-to-digital converter means for coupling to the log detector meansto converting the analog logarithmically detected signal to the spectraldepiction of the RF output.
 23. The RF amplifier system of claim 22,wherein the second means further comprises a second analog-to-digitalconverter means for coupling to the ramp generator means in parallelwith the VCO means to convert the ramp voltage to the spectral depictionof the RF output.
 24. The RF amplifier system of claim 22, wherein theramp generator means is further for coupling to the analog-to-digitalconverter means and the ramp generator means is further to produce ablanking signal of a known interval simultaneously with a zero VDC pointof a signal from the ramp generator means that is fed into the output ofthe log detector means.
 25. The RF amplifier system of claim 24, furthercomprising a microprocessor means for coupling to the ramp generatormeans to control the production of the blanking signal.
 26. The RFamplifier system of claim 21, wherein the third means allows a computerto be connected by an internet connection.